Simultaneous Determination and Stability Analysis of Ten New Psychoactive Substances including Synthetic Cathinones, Phenethylamines, and Ketamine Substitutes in Urine Using Liquid Chromatography-Tandem Mass Spectrometry

Table 3

Lower limit of quantification (LLOQ), calibration curve, correlation coefficient (R²), precision, and accuracy of all analytes in urine by LC-MS/MS.

Analytes	LLOQ (ng/mL)	Calibration curve (ng/mL)	R ^2	Intraday precision; (n = 5, %CV)			Interday precision; (n = 5, %CV)			Accuracy (%); (n = 5)
				25 ng/mL	50 ng/mL	75 ng/mL	25 ng/mL	50 ng/mL	75 ng/mL	25 ng/mL	50 ng/mL	75 ng/mL
Mephedrone	6.3	6.3–100.0	0.9969	5.66	3.85	3.08	2.23	4.16	2.31	100.00	101.20	108.80
Butylone	6.3	6.3–100.0	0.9991	1.80	3.27	4.37	6.63	1.90	5.81	99.20	100.40	97.80
Pentylone	6.3	6.3–100.0	0.9984	2.83	3.59	3.24	4.87	9.21	4.66	100.00	99.60	98.40
Eutylone	3.1	3.1–100.0	0.9986	4.90	2.30	3.09	4.83	3.03	5.20	100.00	96.20	98.40
Ephylone	6.3	6.3–100.0	0.9994	3.64	2.95	3.37	8.33	9.15	9.30	98.40	100.40	98.40
4-MEAPP	3.1	3.1–100.0	0.9991	3.37	2.83	3.75	4.53	7.35	4.04	99.20	100.00	97.33
PMA	6.3	6.3–100.0	0.9990	4.67	1.08	1.20	5.48	9.58	3.04	97.60	101.20	99.47
PMMA	6.3	6.3–100.0	0.9997	2.23	1.77	0.94	8.70	6.96	5.24	98.40	100.80	100.00
DCK	6.3	6.3–100.0	0.9997	0.89	0.90	2.00	3.52	3.04	4.34	101.60	99.96	98.93
2-FDCK	3.1	3.1–100.0	0.9994	2.83	2.60	2.87	2.23	4.66	3.56	100.00	101.87	98.67

LC-MS/MS: liquid chromatography-tandem mass spectrometry; mephedrone: 4-methylmethcathinone; ephylone: N-ethylpentylone; 4-MEAPP: 4-methyl-α-ethylaminopentiophenone; PMA: para-methoxyamphetamine; PMMA: para-methoxymethamphetamine; DCK: deschloroketamine; 2-FDCK: 2-fluorodeschloroketamine; CV: coefficient of variation.